Tribology Letters

, 64:7 | Cite as

Real-Contact Area Between an Elastomer and a Flat Plane Observed by Surface Plasmon Resonance: Optical Model Calculations

  • Satoru Maegawa
  • Hiroshige Matsuoka
  • Shigehisa Fukui
  • Fumihiro Itoigawa
  • Takashi Nakamura
Original Paper


This study presents a novel method for high-sensitivity measurement of the area of the real contact between an elastomer surface and a rigid flat plane, using the surface plasmon resonance (SPR) technique in the Kretschmann configuration. Through numerical calculations, the sensitivity of the SPR method for determining the real-contact area is discussed and compared to other typical optical techniques, such as total internal reflection and multiple beam optical interference. The wavelength dependence of the optical reflectance is simulated, as well as its change with the elastomer-plane gap thickness and the optical properties of the gap material. Non-transparent elastomers are also studied. Consequently, it was found that the SPR method has the highest sensitivity for the measurement of real-contact area; it can detect, for example, an ultra-thin air gap (or water gap) formed between the contacting surfaces from the measurement of the intensity of reflected light from the contact region.


Real-contact area Surface plasmon resonance Soft elastomer Kretschmann configuration 

List of Symbols


Amplitude of the incident light electric field


Amplitude of the reflected light electric field


Resultant electric vector of all positive-going light waves


Resultant electric vector of all negative-going light waves


Complex refractive index




Difference in reflectance


Gap thickness


Maximum gap thickness


Characteristic decay length of evanescent electromagnetic field


Sensitivity factor


Refractive index


Effective refractive index


Difference in effective refractive index


Effective reflection coefficient


Fresnel reflection coefficient


Extinction coefficient


Phase change


Incident angle




Resonance wavelength in the reflectance spectrum in the SPR method


Peak wavelength in the reflectance spectrum in the OIF method


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Copyright information

© Springer Science+Business Media New York 2016

Authors and Affiliations

  • Satoru Maegawa
    • 1
  • Hiroshige Matsuoka
    • 1
  • Shigehisa Fukui
    • 1
  • Fumihiro Itoigawa
    • 2
  • Takashi Nakamura
    • 2
  1. 1.Department of Mechanical and Aerospace EngineeringTottori UniversityTottoriJapan
  2. 2.Department of Mechanical EngineeringNagoya Institute of TechnologyNagoyaJapan

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